Spectroscopy, from initiation to performance
24 052,80 € incl. VAT - 20 044,00 € excl. VAT
The eShel III spectrograph is a professional-grade, multi-wavelength fibre-optic instrument.
When it is not possible to choose between resolution and spectral range, as is the case, for example, in the study of exoplanets, an Echelle spectroscope is required, as it provides numerous high-resolution orders (R = 10,000).
The eShel spectroscope covers a range of approximately 370 to 910 nm (orders 25 to 60).
The complete eShel system comprises the spectroscope itself, as well as the guide cap (F/6), the calibration module (with ThAr lamp), the high-voltage power supply and the optical fibres (20 m long).
| Description | Shelyak ref. | Included |
Acc. type
|
Cooled
|
Comment
|
| Camera Atik 460EX Mono | SE0124 | Camera Science | yes | The standard CCD camera for the eShel II | |
| Caméra ASI2600MM-Pro | EL0271 | Camera Science | yes | New generation CMOS camera |
The eShel III spectroscope enables work across a wide spectral range (370 to 910 nm) at high resolution (R = 10,000). This is made possible by the use of multiple orders (in this case, between 25 and 60); an Echelle spectrum can be read ‘like a book’: the end of one order is found at the start of the next.
The decision was taken to adopt a fibre-optic solution in order to improve the accuracy of radial velocity measurements (the instrument is separate from the telescope, ideally housed in a temperature-controlled room, and is therefore not subject to any flexure) and to enhance user comfort.
We have developed this instrument based on our experience with the Musicos and Narval professional spectroscopes.
This technique enables high spectral resolution to be achieved as it use the higher diffraction orders of a diffraction grating. The resulting spectrum passes through a cross disperser, which “slices” the spectrum into successive orders, occupying the entire surface of the camera’s sensor. In this way, the entire spectral range in the visible spectrum is obtained over some twenty orders (in the case of the eShel).
Schematic diagram of an Echelle spectrograph (© François Cochard)
This is the main module that generates the Echelle spectrum. It covers the spectral range from approximately 370 to 910 nm with a resolution of R=10,000 (using an ASI 2600 MM Pro camera, not included). It has an FC/PC connector for attaching 50 µm object fiber. 
Example using the solar spectrum
Sunlight spectrum
Orders #22 through #61 are uniformly focused.
Spectrum of Chi Oph Be star
This allows us to process orders #25 through #60 and extend the usable spectral range from approximately 370 to 910 nm. 
The motorised version of this lens comes with a PrimaLuce Lab focuser, which allows for remote focusing (ideal for remote operation or when the spectrograph is not located next to the control PC).
There is also a manual version fitted with a helical focuser.
CEO of Shelyak Instruments eShel III in few words The eShel III spectroscope is one of the flagship instruments in the Shelyak Instruments product line. This is the third generation of this instrument, which combines high resolution with a wide spectral range. This...
By Olivier Garde The eShel II spectroscope features an 85-mm focal-length camera lens that is no longer manufactured; an alternative had to be found, so Shelyak Instruments designed its own 122-mm focal-length Petzval-type lens. This “custom” design has made it...
You'll find all our Demetra video tutorials on this web page. Demetra is a free software package for processing spectra from the ALPY 600, LISA and eShel spectrographs from the Shelyak Instruments range. Playlist of Demetra tutorials Tutorial #1 Introduction to...
